Windows constructed from multiple glass panes utilized “muntins” or “muntin bars” to secure the edges of the individual glass panes within the window sash. In many windows, muntins formed distinctive grid patterns that are associated with architectural styles of buildings containing the windows.
Modern windows formed by insulating glass units utilize single glass lites separated by an insulating air space. Where a particular architectural “look” is desired, a grid of muntin bars is fixed in the air space between the glass lites to simulate a multipane window. Typical muntin bars for insulating glass units are formed from decoratively coated interfitted metal tubes. The grids are anchored to the insulating glass unit periphery.
Muntin bar stock is produced by roll forming decoratively coated sheet material such as aluminum or steel, in a known manner. Various sizes of the sheet material are used to form different size muntin bar stock. The roll forming machine has a series of rolls configured to form sheet material into elongated tubular muntin bar stock. A window manufacturer purchases the muntin bar stock size(s) needed to produce insulating glass units, cuts the stock into lengths that are notched and assembled into grids for incorporation into the insulating glass units.
The cut-to-length muntin bars are then fed to a notching device to form notches that will be located at the muntin bar intersections. Although some machinery may be specialized to notch the bars for forming grids, the muntin bars typically must be manually handled to produce correctly sized muntin bars with properly located notches.
U.S. Pat. No. 6,173,484 to McGlinchy et al discloses a system for fabricating muntin bars from sheet material. Sheet material in the form of thin ribbon stock is fed to a first forming station including a punching mechanism that punches the ribbon stock at a precisely predetermined location. The ribbon stock is delivered from the first forming station to a second forming station in the form of a rolling mill. The stock passes through a succession of forming rolls to produce a tube having a desired cross-sectional shape. The tube is delivered from the second forming station to a third forming station including a severing apparatus that severs the tube at a precisely predetermined location to produce a muntin bar. After severing, the muntin bar is engaged by a conveyor and moved to a desired location.
U.S. Pat. No. 6,651,304 to McGlinchy et al discloses a method and apparatus for making a contoured muntin bar. A supply of sheet material having a finished surface on at least one side in the form of a coiled ribbon is unwound and fed along a strip path of travel to a punch station. At the punch station a ribbon punching mechanism punches the ribbon at a precisely predetermined locations along the ribbon to form one of a plurality notch patterns that define a portion of a contoured muntin bar. Downstream along the travel path from the punch station the ribbon is fed through a forming station having a succession of forming rolls that define a succession of forming roll nips to bend the ribbon and form a generally closed cross-sectional tube. The rolls form a number of bending stages to produce a muntin bar tube having a contoured shape with raised sides to provide an attractive appearance to a muntin grid.
U.S. Pat. No. 5,099,626 to Seeger concerns a connecting connector for connecting hollow muntin bars transversely to each other and includes barbed projections or hooks which engage openings in plan sides of a tubular muntin bar.
U.S. Pat. No. 6,244,012 concerns a muntin bar joiner for connecting muntin bars in a grid. The muntin bar comprises a relatively flat, thin body, a first muntin bar engagement leg extending from one end of the body, a second muntin bar engagement leg extending from an opposite end of the body, and first and second abutments extending from the body. The muntin bar engagement legs extend along a longitudinal axis of the joiner and the first and second abutments extend from the body transverse to the axis. Each abutment comprises a muntin bar abutment face oriented in a direction transverse to the axis, with the abutment faces facing in opposite axial directions. The disclosed joiner has opposite body sides that define substantially parallel major surfaces and opposite edges that are substantially parallel and extend substantially parallel to the axis. Different embodiments are disclosed in which the abutments extend from body sides or body edges. The disclosure of the '012 is incorporated herein by reference.